Maternity Nursing: cram pack

Formula sheets, the key method steps for every topic and 6 practice problems, with full solutions at the back.

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1Formulas and methods

Maternity & obstetric nursing

Method

  1. Place the woman in time: weeks of pregnancy, stage of labour or day after birth, and decide what is normal at that point.
  2. Look for the patient in danger: the mother, the fetus or the newborn, or more than one of them.
  3. Link the finding to its cause: VEAL CHOP for decelerations, the four Ts for bleeding, BUBBLE-HE after birth.
  4. Choose the action that improves blood flow and oxygen first (side-lying, stopping oxytocin, fundal massage), then escalate.

Dosage calculations

Dose from strength
volume = dose / strength
Weight-based dose
dose = mg/kg × body weight
Tablets
number = dose / tablet strength
Units
1 g = 1000 mg, 1 mg = 1000 mcg

Method

  1. Convert the ordered dose and the stock strength to the same unit.
  2. Use desired over have times quantity: (D/H) × Q.
  3. For weight-based doses, multiply by the weight in kg first, then divide the daily dose by the number of doses.
  4. Estimate first and check that the answer is reasonable.

IV infusion rates

Pump rate
mL/h = volume (mL)/time (h)
Drip rate
drops/min = volume (mL) × drop factor / time (min)
Infusion time
time (h) = volume (mL)/rate (mL/h)

Method

  1. Pump rate in mL/h: volume divided by time in hours.
  2. Drip rate in drops/min: volume × drop factor divided by time in minutes.
  3. For time remaining: volume left divided by the rate.
  4. Round as the question or the equipment requires.

2Practice problems

1.Maternity & obstetric nursingMedium

At 30 weeks, which fundal height is consistent with expected growth?

  1. A22 cm
  2. B29 cm
  3. C36 cm
  4. D18 cm
2.Maternity & obstetric nursingHard

A pregnant woman with chronic hypertension takes lisinopril. Why should the nurse alert the prescriber?

  1. AACE inhibitors can harm fetal kidney development and are avoided in pregnancy
  2. BLisinopril will cause her blood pressure to rise in pregnancy
  3. CACE inhibitors cause neural tube defects only in the third trimester
  4. DLisinopril is the first-choice antihypertensive in pregnancy
3.Dosage calculationsMedium
22 kg30 mg/kg/day4× per dayD = ? mg

A patient weighs 22 kg. The prescribed dose is 30 mg/kg per day, given in 4 equal doses. How many milligrams D are given per dose?

22 kg30 mg/kg/day4× per day
D = mg
4.Dosage calculationsHard
00.10.20.30.40.50.60.70.80.911 mL

The prescription is 720 units of a drug that comes as 1000 units/mL. Draw up the dose in the 1 mL syringe: what volume V do you give?

720 units1000 units/mL
V = mL
5.IV infusion ratesMedium
500 mL20 gtt/mL5 h? gtt/min

Infuse 500 mL over 5 hours with a giving set of 20 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

500 mL5 h20 gtt/mL
R = gtt/min
6.IV infusion ratesHard
2 g500 mL? mL/h0.5 mg/min

A bag contains 2 g of a drug in 500 mL. The order is 0.5 mg per minute. At what rate R do you set the pump, in mL/h?

2 g/500 mL0.5 mg/min
R = mL/h

3Solutions

1.Maternity & obstetric nursing

Answer: B · 29 cm

Why this is the answer

The expected fundal height at 30 weeks is about 28–32 cm. A difference of more than 2–3 cm from the gestational age should be followed up, usually with an ultrasound.

Answer

B · 29 cm
2.Maternity & obstetric nursing

Answer: A · ACE inhibitors can harm fetal kidney development and are avoided in pregnancy

Why this is the answer

ACE inhibitors are fetotoxic, especially in the second and third trimesters, causing fetal kidney damage and oligohydramnios. Labetalol, nifedipine or methyldopa are used instead.

Answer

A · ACE inhibitors can harm fetal kidney development and are avoided in pregnancy
3.Dosage calculations

Answer: D = 165 mg

Dose calculation: the amount to give equals what is prescribed divided by what you have, times the quantity it comes in: amount = (desired dose/stock strength) × stock volume. Always keep the units the same (convert g to mg, mg to mcg first) and check that the answer is sensible.

Total per day

30·22 = 660 mg

Per dose

D = 660/4 = 165 mg

Answer

D = 165 mg
4.Dosage calculations

Answer: V = 0.72 mL

Drawing up a dose: volume = (prescribed dose/stock strength) × stock volume. Convert to the same units first, then check that the volume fits the syringe and lands on one of its graduations.

Volume

V = 720/1000 = 0.72 mL

On the syringe

On this 1 mL syringe every small line is 0.01 mL.

Answer

V = 0.72 mL
5.IV infusion rates

Answer: R = 33 gtt/min

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Time in minutes

5·60 = 300 min

Drip rate

R = 500·20/300 = 33.33 ≈ 33 gtt/min

Answer

R = 33 gtt/min

At the bedside you round to the nearest whole drop: 33 gtt/min.

6.IV infusion rates

Answer: R = 7.5 mL/h

Dose-based infusions: concentration = amount of drug in the bag/bag volume. Pump rate (mL/h) = dose per hour/concentration, and dose per hour = mL/h × concentration. Convert per-minute doses to per-hour (× 60) and keep the mass units the same (1 g = 1000 mg, 1 mg = 1000 mcg).

Concentration

2000 mg/500 mL = 4 mg/mL

Dose per hour

0.5·60 = 30 mg/h

Pump rate

R = 30/4 = 7.5 mL/h

Answer

R = 7.5 mL/h

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